The present invention relates to heterocyclic-cyclic amine derivatives of the formula I below, and pharmaceutically acceptable salts of such compounds. The compounds of formula I are cholinesterase inhibitors and are useful in enhancing memory in patients suffering from dementia and Alzheimer's disease.
Alzheimer's disease is associated with degeneration of cholinergic neurons in the basal forebrain that play a fundamental role in cognitive functions, including memory, Becker et al., Drug Development Research, 12, 163-195 (1988). As a result of such degeneration, patients suffering from the disease exhibit a marked reduction in acetylcholine synthesis, choline acetyltransferase activity, acetylcholinesterase activity and choline uptake.
It is known that acetylcholinesterase inhibitors are effective in enhancing cholinergic activity and useful in improving the memory of Alzheimer's patients. By inhibiting acetylcholinesterase enzyme, these compounds increase the level of the neurotransmitter acetylcholine, in the brain and thus enhance memory. Becker et al., supra, report that behavioral changes following cholinesterase inhibition appear to coincide with predicted peak levels of acetylcholine in the brain. They also discuss the efficacy of the three known acetylcholinesterase inhibitors physostigmine, metrifonate, and tetrahydroaminoacridine.
European Patent Application EP A 0 229 391 relates to piperidine derivatives of the formula: R.sup.1 --X--A--R.sup.2. European Patent Application EP A 296 560 relates to a cyclic amine compound of the formula ##STR2##
All documents cited herein, including the foregoing, are incorporated herein in their entireties.